What makes Ripley work?

Back in 1979, few women were working as truckers or worked with machinery, although women were gradually starting to work in those fields at that time. The crew of the Nostromo are often described as "space truckers". I imagine they did some mining as well. The crew includes not one but two women, and this fact alone suggests that the trends of women (circa 1979) slowly moving into these fields would continue into the future. Unlike most sci-fi movies from the 50's say, they weren't depicted as "hot babes" with bouffant hair dos fainting left and right. So, in that sense, the film was reflecting the women's lib movement of it's time, but why wouldn't it?

The Ripley character in Alien and Aliens works because it everything she does in the movie is logically built off of the types of skills she would have and the type of job(s) she did. Clearly, as a warrant office she was highly capable, experienced and had well-developed skills. She isn't a science officer, so her line of work clearly was of a practical hands-on nature. She is shown of being tough and capable of standing her ground, but a man in her position would have to do the same, which considering she was second in command only makes sense. Lambert obviously wouldn't be cut out for a leadership post, although I'm sure she was capable enough in her position on the ship. In the sequel Aliens, it is revealed that (a) Ripley is a mother, and that her child has died while she was in stasis, and (b) she is a capable fork lift operator. Her skill with the fork lift is entirely logical also, given that the Nostromo is a mining ship and she would have used this type of machinery logically in her work. So when it is revealed she is good at using that machine, it isn't jarring in the same way that Rey in Star Wars is suddenly good at flying the Millennium Falcon or using a light saber. Those are not logical skills for her Rey to have, Ripley's skills DO make sense. Ripley can't use a weapon at first, but she is how to use one by a Marine who does. Again, since she is skilled in the use of machinery and likely picks up things quickly, it is not surprising that she becomes proficient in firearms. Her maternal desire to both protect Newt and make up for the daughter she lost make her actions in the second act entirely believable. Beside, she was the only person who had previously experienced and survived the xenomorphs.

Sigourney is a great actress and the film doesn't force the 'strong female' message. Many newer films will beat you over the head with the fact they're a female and they're badass.

Ripley comes across as intelligent, dutiful and ultimately as someone who isn't trying to showoff or prove a point.

I might be remembering this wrong, but didn't most of the characters start off with equal roles and screen times? Starting the entire cast off on equal footing and have them slowly dwindle down to the last one standing might work better than starting the movie off with a main character needing an arc.